Path Cardioresp: investigating resp outbreak in ruminants

What to check during group clinical examination

• increased respiratory rates

• Behavioural change - ear position, not rising

• Evidence of open mouth breathing

• Coughing

• Examine proportion of the group further

What to check during individual clinical exam when investigating resp disease in ruminants

Body condition score

Respiratory rate and lung auscultation

Pyrexia

ID affected age group

Estimate the number affected with clinical signs

Normal respiratory and heart rate, and rectal temperature of sheep

Resp = 16-34

Heart = 70-80

Temp = 38.3-39.9

Normal respiratory and heart rate, and rectal temperature of cattle

Resp = 26-50

Heart = 48-84

Temp = 38-39.3

What pattern of lung pathology? Describe it. 2 example causes and possible differential

Suppurative bronchopneumonia (bacterial)

Neutrophilic inflammation

Cranioventral lung reddening, due to consolidation

Examples: Pasteurella multocida, Mycoplasma

Ddx = aspiration pneumonia

What pattern of lung pathology? (2 names). Describe it. 1 example cause.

Fibrinous bronchopneumonia or Lobar pneumonia/pleuropneumonia

Fibrinous exudate predominates in the cranioventral lung/consolidation

Cause: Mannheimia haemolytica

What pattern of lung pathology? Describe it. 2 example causes.

Interstitial pneumonia

Affects alveolar and interlobular septae.

Lungs fail to collapse

Rib impressions

Lacks visible exudates

Rubbery/elastic/meaty texture

Causes: Maeda Visna virus, fog fever/acute bovine pulmonary emphysema

What are these lung patterns together? Describe it. 3 example causes.

Bronchointerstitial pneumonia.

Affects cranioventral lung lobes with bronchopneumonia, and the alveolar and interlobular septae

Causes:

• Bovine respiratory syncytial virus

• Parainfluenza 3

• Mycoplasma bovis

What pattern of lung pathology? Describe appearance and pathogenesis. 2 example causes.

Embolic pneumonia

Multifocal random distribution on all lobes

Caused by haematogenous injury on arterioles/capillary beds = trapping bacterial emboli

Can progress into abscesses

Causes:

• Omphalophlebitis (umbilical infection)

• Vegetative endocarditis

What pattern of lung pathology? Describe appearance and pathogenesis. 3 example causes.

Granulomatous pneumonia

Caused by aerogenous or haematogenous injury by particles that cannot be eliminated or phagocytosed.

Randomly distributed granulomas.

Macrophages predominate. Giant multinucleated cells possible.

Causes: Mycobacterium bovis

Parasite migration e.g. liver fluke

Aspergillus/systemic fungal infection

What pattern of lung pathology? Describe appearance and pathogenesis. Example cause (cattle)

Tumour metastases - secondary to malignant neoplasm elsewhere.

Unusual in farm species.

Causes multiple randomly distributed lesions throughout all lobes.

Lesions have variable size and appearance depending on cell type.

Cause: Lymphoma - Enzootic Bovine Leukosis (notifiable)

What pattern of lung pathology? Describe appearance and pathogenesis. Give an example cause.

Primary neoplasia with metastasis.

Random or cranioventral distribution.

Often has secondary bacterial infection.

Variable size and shape

Firm grey/cream mass

Cause: Ovine Pulmonary Adenocarcinoma/Jaagsiekte retrovirus

What pattern of lung pathology? Describe appearance. Give example cause in pigs.

Dorsal diaphragmatic pneumonia

Locally extensive distribution on dorsal aspect of caudal lung lobes

Well demarcated areas of necrosis when cut

Cause: Actinobacillus pleuropneumonia (APP)

What pattern of lung pathology? Describe appearance. Give 3 example causes.

Verminous pneumonia

Locally extensive consolidation of dorsal caudal lung lobe

Adult worms present in bronchus

Pneumonia can be: interstitial (migration), chronic bronchitis (adults in airways) or granulomatous (dead parasite/larvae)

Causes: Dictyocaulus viviparus (cattle), Dictyocaulus filaria (significant, sheep), Muellerius capillaris (incidental, sheep)

What pattern of lung pathology? Describe it and pathogenesis. 4 example causes and 1 differential diagnosis.

Aspiration pneumonia

Usually cranioventral and unilateral.

Caused by foreign material reaching lung through inhalation. Can cause septic or gangrenous pneumonia.

Causes:

• Stomatitis (pharyngitis/laryngitis)

• Regurgitation of ruminal contents

• Metabolic disorders

• Iatrogenic (feeding tube_

Differential = suppurative bronchopneumonia

What is this?

Hypostatic congestion.

Normal post mortem change caused by pooling of blood. Depends on how the carcass is laying down

Helps demonstrate rib impressions if lungs fail to deflate (MV)

Will float as air spaces still present. Blood is pooling in capillaries.

What lung histopathology samples should be taken at post mortem?

1cm strips of lung.

3 sections from 3 different lobes

Include edge of lesion with some normal tissue

1:10 tissue: formalin ratio

Same sample to be frozen

What are the diagnostic samples and tests are used for bacterial disease?

Bronchoalveolar lavage or tracheal wash/nasopharyngeal swab in cattle

Aseptic technique on post mortem samples - bacteriological swabs

• lung - boarder of affected and unaffected lung, or middle of affected tissue if on antibiotics

• sample from heart blood or liver - septicaemia

• centre of abscess

• Cranioventral lung tissue for PCR if Mycoplasma suspected

Histopathology of samples

What diagnostic tests and samples are used for viral diseases?

Use sterile dry swab. Not charcoal, or wooden.

Sample spleen for bovine viral diarrhoea virus PCR

Sample clotted blood post mortem for serology of MV in sheep

Histopathology

What diagnostic tests and samples are used for parasitic disease?

Baermann test = separates lungworm larvae from faecal material (live animal)

Histopathology to show larvae/other stages, infiltrating eosinophils within pulmonary parenchyma.